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SDI stands for serial digital interface and contains a package of digital video interfaces first standardized by SMPTE (The Society of Motion Picture and Television Engineers) in 1989.
Additional SDI standards have been introduced to support increasing video resolutions (HD, UHD and others), frame rates, three dimensional videos and color depth. Dual link HD-SDI consists of a pair of SMPTE 292M links, standardized by SMPTE 372M in 1998 3G-SDI (standardized in SMPTE 424M) consists of a single 2.970 Gbit/s serial link that allows replacing dual link HD-SDI, newer standards 6G-SDI and 12G-SDI were published on March 19, 2015.
These standards are used to transmit uncompressed, unencrypted digital video signals (optionally including embedded audio and time code) within television facilities. They can also be used for transmitting packetized data. Coaxial variants of the specification range in length but are typically less than 300 meters. Fiber optic variants of the specification such as 297M allow for long-distance transmission limited only by maximum fiber length. SDI and HD-SDI are usually available only in professional video equipment because various licensing agreements restrict the use of unencrypted digital interfaces, such as SDI, prohibiting their use in consumer equipment. Several professional video and HD-video capable DSLR cameras and all uncompressed video capable consumer cameras use the HDMI interface, sometimes called clean HDMI or unencrypted HDMI.
Recommendation G.694.2 defines 18 channels of CWDM, from 1271 nm to 1611 nm, with channel spacing equal to 20 nm (it is worth noting the mutual shift of the nominal central wavelengths of lasers and CWDM filters by 1 nm, in order to symmetry the temperature window). Traditionally, the 1371 nm and 1391 nm channels have been rarely used, due to the occurrence of the so-called "white light" water peak in old type fiber optics. At present, however, the quality of G.652.D standard fibers allows to use full 18 channels of CWDM. In some situations the use of low channels (1271 nm and 1291 nm) may be problematic, as some G.652.D fibers of low quality may not guarantee homogeneity in this region. Application of CWDM transmission on other types of single-mode fibers (e.g. G.655) requires attention and caution, as not all CWDM channels can be supported due to dispersion properties, spectral damping profile or cut-off wavelength.
• Compatible with any Serial Digital Signal up to 3.0 Gbps
• Available with internal optics for use with a single optical fiber
• Standardized channels for both CWDM bands for compatibility with Python™ systems
• Passes SDI embedded audio and all ancillary data
• Input equalization and reclocking for SDI video on buffered outputs
• Available in any custom configuration for Bi-Directional Transport up to 16 total channels
• Real-time status LED indicators for troubleshooting and monitoring
• DWDM systems available by request for higher density systems
• Compatible with any Serial Digital Signal up to 3.0 Gbps
• Available with internal optics for use with a single optical fiber
• Standardized channels for both CWDM bands for compatibility with Python™ systems
• Passes SDI embedded audio and all ancillary data
• Input equalization and reclocking for SDI video on buffered outputs
• Available in any custom configuration for Bi-Directional Transport up to 16 total channels
• Real-time status LED indicators for troubleshooting and monitoring
• DWDM systems available by request for higher density systems
The length of the CWDM link in most cases is limited by the power budget. In rare cases, a dispersion restriction is also important for 10G lines. The available power budget for 1G lines is up to 40 dB, for 10G lines it rarely exceeds 24 dB. Although typically CWDM links use two transmission fibers (each for one-way signal transmission), it is possible to combine a duplex CWDM link on a single fiber. In most cases, this means halving the capacity of the link (i.e. the possibility of combining up to 9 duplex transmissions instead of the normally available 18). The CWDM system allows the use of lasers without a thermoelectric cooling element, which leads to lower costs compared to a DWDM system. Thor Fiber offers up Simplex units for simplicity in throw down situations and applications where fiber is hard to comeby.